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-   -   DC or AC motor? (http://www.knifenetwork.com/forum/showthread.php?t=69002)

M&J 03-24-2020 01:43 AM

DC or AC motor?
 
The 1.5 HP DC Baldor went down. The commutator had all kinds of carbon fouling so I took the back end apart to clean and re-assembled. Nada. Thought the VS controller was bad but it tested fine. :(

Considering this DC Leeson as a replacement since I can still use the VS controller.
http://www.electricmotorwholesale.com/LEESON-109096/

Scott at Tru Grit suggested the AC over the DC motors but I'm unfamiliar with those types...school me?

R K 04-14-2020 08:14 PM

208 3ph with VFD
 
For many years, I used a 2HP DC Baldor on my knife grinder.. Now I use a 3hp, 3ph 208V AC motor with a VFD (Variable Freq Drive)
The AC motor with a VFD is light years ahead of the DC motor/controller.
The DC only has full power at full speed, as you decrease speed you decrease power because you are decreasing speed by decreasing voltage.
The AC motor speed is controlled by varying the 3 phase frequency, thus you loose very little if any power as you decrease speed.
I have two knife grinders in my shop and both use the 208V AC motors with the VFD controllers. I can't imagine ever going back to DC.
A couple years ago, I found seven Baldor DC controllers and two 2HP Baldor motors at the dump, as it turns out, a packing plant near here was retrofitting with the new 208V AC units. Now I use the DC units on my disc sanders.
IMHO, I wouldn't even consider a DC motor for a grinder now!
RK

M&J 04-18-2020 02:06 PM

The controller which I originally thought was dead still functions. I'd called Scott at Tru Grit and we discussed the set-up. Going AC would be cool yet in these times more $ than I want to spend at ~$1,200. A new Leeson 1HP DC motor was ~$450.

fmustang1981 04-06-2021 05:49 PM

I would also take a DC motor. Personally, this was the right decision for me, as I needed to have speed control and output range, while the AC motor was a little more powerful, but it was less responsive. I think this is one of the main differences between these motors and everyone will choose what will be more profitable for him. I also had a bad experience with AC motors as the only model that I have constantly failed for various reasons. Often this was due to electronics failure. I had to buy quality parts here https://www.automation-usa.com/ and make substitutions since what I had then was very unreliable.

M&J 04-07-2021 12:17 AM

I'm also inclined to get a DC motor. I miss having two machines and for now making due with one.


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